The present invention relates to an electron-emitting device manufacturing method and apparatus, driving method, and adjusting method thereof.
Conventionally, electron-emitting devices are mainly classified into two types of devices: thermionic and cold cathode electron-emitting devices. Known examples of the cold cathode electron-emitting devices are field emission type electron-emitting devices (to be referred to as FE type electron-emitting devices hereinafter), metal/insulator/metal type electron-emitting devices (to be referred to as MIM type electron-emitting devices hereinafter), and surface-conduction type of electron-emitting devices (to be referred to as SCE type electron-emitting devices hereinafter.
Known examples of the FE type electron-emitting devices are disclosed in W. P. Dyke and W. W. Dolan, xe2x80x9cField emissionxe2x80x9d, Advance in Electron Physics, 8, 89 (1956) and C. A. Spindt, xe2x80x9cPHYSICAL Properties of thin-film field emission cathodes with molybdenum conesxe2x80x9d, J. Appl. Phys., 47, 5248 (1976).
A known example of the MIM type electron-emitting devices is disclosed in C. A. Mead, xe2x80x9cOperation of Tunnel-Emission Devicesxe2x80x9d, J. Appl. Phys., 32,646 (1961).
A known example of the SCE type electron-emitting devices is disclosed in, e.g., M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965).
The SCE type device utilizes the phenomenon that electrons are emitted from a small-area thin film formed on a substrate by flowing a current parallel through the film surface. The SCE type electron-emitting device includes electron-emitting devices using an SnO2 thin film according to Elinson mentioned above [M. I. Elinson, Radio Eng. Electron Phys., 10, 1290, (1965)], an Au thin film [G. Dittmer, xe2x80x9cThin Solid Filmsxe2x80x9d, 9,317 (1972)], an In2O3/SnO2 thin film [M. Hartwell and C. G. Fonstad, xe2x80x9cIEEE Trans. ED Conf.xe2x80x9d, 519 (1975)], a carbon thin film [Hisashi Araki et al., xe2x80x9cVacuumxe2x80x9d, Vol. 26, No. 1, p. 22 (1983)], and the like.
The FE, MIM, and SCE type electron-emitting devices have an advantage that many devices can be arranged on a substrate. Various image display apparatuses using these devices have been proposed.
It is known that characteristic changes in actual driving can be suppressed by applying a voltage higher than a voltage applied in the actual driving in the manufacturing process of the SCE type electron-emitting device.
An image display apparatus formed using the electron-emitting devices must maintain brightness and contrast suitable for image display over a long term.
To realize this, the electron-emitting device must emit a predetermined electron amount or more in an expected term, while suppressing a decrease in electron amount emitted by the electron-emitting device.
However, the conventional electron-emitting device gradually decreases the electron emission amount along with long-term driving at a constant driving voltage.
In any type of electron-emitting device described above, the field strength near the electron-emitting portion is high during the actual driving. Changes over time near the electron-emitting portion arising from a high field strength is considered to decrease the electron emission amount.
It is an object of the present invention to provide an electron-emitting device manufacturing method and driving method capable of suppressing changes over time in characteristics of an electron-emitting device and, more particularly, to provide an electron-emitting device manufacturing method and driving method capable of suppressing a decrease over time and unstableness in the electron emission amount from the electron-emitting device.
An electron-emitting device manufacturing method according to the present invention has the following steps.
That is, there is provided a method of manufacturing an electron-emitting device which has at least two electrodes and emits electrons by applying a voltage between the two electrodes, comprising:
the voltage application step of applying a voltage V1 between the two electrodes, the voltage V1 being a voltage having a relationship with a maximum voltage value V2 applied to the electron-emitting device as a normal driving voltage after the voltage application step, so as to satisfy
giving a current I flowing upon application of a voltage V when the voltage V falling within a voltage range causing electron emission upon application of the voltage between the two electrodes is applied between the two electrodes:
I=f(V)xe2x80x83xe2x80x83(1)
and letting fxe2x80x2(V) be a differential coefficient of f(V) at the voltage V,
a first condition:
f(V1)/{V1xc2x7fxe2x80x2(V1)xe2x88x922f(V1)} greater than f(V2)/{V2xc2x7fxe2x80x2(V2)xe2x88x922f(V2)}xe2x80x83xe2x80x83(2)
wherein the voltage application step satisfies a second condition, upon completion of the voltage application step,
wherein the second condition is defined by letting Xn-1 be a value of a right side, i.e., f(V2)/{V2xc2x7fxe2x80x2(V2)xe2x88x922f(V2)} of the inequality (2) upon a first application of the pulse-like voltage V2 when the voltage V2 is applied as pulses successively twice between the two electrodes upon completion of the voltage application step, and Xn be a value of the right side, i.e., f(V2)/{V2xc2x7fxe2x80x2(V2)xe2x88x922f(V2)} of the inequality (2) upon a second application of the pulse-like voltage V2,
wherein Xn-1 and Xn satisfy:
(Xn-1xe2x88x92Xn)/Xn-1xe2x89xa60.02xe2x80x83xe2x80x83(A)
The second condition is that Xn-1 and Xn satisfy:
(Xn-1xe2x88x92Xn)/Xn-1xe2x89xa60.01xe2x80x83xe2x80x83(B)
The electron-emitting device manufactured through the voltage application step hardly changes its characteristics upon long-time application of the maximum voltage value V2 applied in actually driving the electron-emitting device (normally using it). The current I flowing upon application of the voltage V when the voltage V falling within a voltage range causing electron emission upon application of the voltage between the two electrodes is applied between the two electrodes is a current emitted upon application of the voltage V or a current flowing between the two electrodes. For example, in an FE or SCE type electron-emitting device, the current I is an emitted current or a current flowing between a pair of electrodes.
In an MIM type electron-emitting device, the current I is an emitted current or a current (diode current) flowing between two electrodes sandwiching an insulating layer. The differential coefficient fxe2x80x2(Vn) of f(Vn) at a given voltage Vn can be obtained as follows. An emission current (or a current flowing between two electrodes) In upon application of the voltage Vn, and an emission current (or a current flowing between the two electrodes) In2 upon application of a voltage Vn2 lower by a small amount dVn than the voltage Vn immediately after or immediately before application of the voltage Vn are obtained, and (Inxe2x88x92In2) is divided by dVn. That is, f(V)/{Vxc2x7fxe2x80x2(V)xe2x88x922f(V)} can be calculated as In/{Vnxc2x7(Inxe2x88x92In2)/dVnxe2x88x922In}.
Especially, the second condition is more preferably a condition that the change rate of Xn, i.e., (Xn-1xe2x88x92Xn)/Xn-1 is 1% or less.
The voltage V1 can be applied by various methods. The magnitude of the voltage V1 is not necessarily constant as long as the voltage V1 satisfies the condition of the inequality (2). The voltage V1 is preferably applied as a pulse-like voltage.
To satisfy the second condition by the voltage application step, a voltage is applied under the same conditions as those adopted in applying the present invention, between two electrodes identical to two electrodes constituting at least part of an electron-emitting device to which the present invention is applied. Xn-1 and Xn are measured for the electron-emitting device obtained in this step, thereby attaining conditions under which Xn-1 and Xn satisfy the inequality (A), and more preferably the inequality (B). For example, when the voltage V1 which satisfies the inequality (2) is applied as pulses a plurality of number of times in the voltage application step, the number of application times of the pulse voltage V1 that can satisfy the second condition is obtained in advance, and the pulse-like voltage is applied the determined number of times in the voltage application step. Alternatively, the duration of the voltage application step that can satisfy the second condition may be obtained in advance, and the voltage application step may be performed for the determined duration. The voltage application step may also be performed while monitoring characteristics to directly or indirectly confirm whether the second condition is satisfied. For example, the second condition is confirmed to be satisfied when the left side of the inequality (2) i.e., the change rate of f(V1)/{V1xc2x7fxe2x80x2(V1)xe2x88x922f(V1)} reaches a predetermined value (e.g., 5% or 3%) or less in the voltage application step. In the voltage application step, the change rate of f(V1)/{V1xc2x7fxe2x80x2(V1)xe2x88x922f(V1)} is obtained every time, e.g., the pulse-like voltage V1 is applied. If the change rate reaches the previously confirmed value or less, the voltage application step ends. Alternatively, the voltage V2 may be actually applied between two electrodes during the voltage application step to confirm whether the second condition is satisfied. Until the second condition is confirmed to be satisfied, the voltage application step and the confirmation step by the application of the voltage V2 may be repeated to realize the voltage application step which satisfies the second condition.
In the manufacturing method of the present invention, the voltage application step is preferably performed in a high-vacuum atmosphere.
In the manufacturing method of the present invention, when the two electrodes sandwich a gap, the voltage application step is preferably performed in an atmosphere in which the gap between the two electrodes is not made narrow by deposition of a substance in the atmosphere or a substance originating from the substance in the atmosphere in the voltage application step.
In the manufacturing method of the present invention, the voltage application step is preferably performed in an atmosphere in which carbon and a carbon compound in the atmosphere have a partial pressure of 1xc3x9710xe2x88x926 Pa or less. The partial pressure is more preferably 1xc3x9710xe2x88x928 Pa or less. The total pressure is preferably 1xc3x9710xe2x88x925 Pa or less, and more preferably 1xc3x9710xe2x88x926 Pa or less.
Assume that the second condition is satisfied if Xn-1 and Xn satisfy (Xn-1xe2x88x92Xn)/Xn-1xe2x89xa60.02 or (Xn-1xe2x88x92Xn) /Xn-1xe2x89xa60.01 in the atmosphere upon the voltage application step.
As described above, two electrodes to which the voltage is applied in the voltage application step are a pair of electrodes of an FE type electron-emitting device (e.g., an emitter cone electrode and gate electrode for a Spindt type electron-emitting device), a pair of electrodes of an SCE type electron-emitting device (e.g., high- and low-potential electrodes), or a pair of electrodes sandwiching an insulating layer in an MIM type electron-emitting device.
The present invention can be preferably applied to an electron-emitting device such as an FE or SCE type electron-emitting device in which a gap is formed between two electrodes to which an electron emission voltage is applied.
The present invention incorporates an electron-emitting device manufacturing apparatus used in the electron-emitting device manufacturing method. This apparatus comprises a potential output portion for applying a voltage between the two electrodes.
An electron-emitting device driving method according to the present invention has the following steps.
That is, there is provided a method of driving an electron-emitting device which has at least two electrodes and emits electrons by applying a voltage between the two electrodes,
wherein the electron-emitting device undergoes the voltage application step of applying a voltage V1 between the two electrodes, the driving method comprises a driving process of driving the electron-emitting device using a maximum value of a normal driving voltage as V2, the voltage V1 is a voltage having a relationship with the voltage V2 so as to satisfy
giving a current I flowing upon application of a voltage V when the voltage V falling within a voltage range causing electron emission upon application of the voltage between the two electrodes is applied between the two electrodes:
I=f(V)xe2x80x83xe2x80x83(1)
and letting fxe2x80x2(V) be a differential coefficient of f(V) at the voltage V,
a first condition:
f(V1)/{V1xc2x7fxe2x80x2(V1)xe2x88x922f(V1)} greater than f(V2)/{V2xc2x7fxe2x80x2(V2)xe2x88x922f(V2)}xe2x80x83xe2x80x83(2)
the voltage application step includes the step of, upon completion of the voltage application step,
letting Xn-1 be a value of f(V2)/{V2xc2x7fxe2x80x2(V2)xe2x88x922f(V2)} upon application of the pulse-like voltage V2 when the voltage V2 is applied as pulses successively twice between the two electrodes upon completion of the voltage application step, and Xn be a value of f(V2)/{V2xc2x7fxe2x80x2(V2)xe2x88x922f(V2)} upon next application of the pulse-like voltage V2,
satisfying a second condition that Xn-1 and Xn satisfy:
(Xn-1xe2x88x92Xn)/Xn-1xe2x89xa60.02xe2x80x83xe2x80x83(A)
The present invention incorporates an adjusting method used for adjustment before shipping in the voltage application step described as the voltage application step in the manufacturing method, or for adjustment after the start of actual use.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.